In many different medical settings, it would be advantageous to be able to detect changes in bodily fluid composition and distribution as they occur, in a noninvasive manner. For example, it is often critical to monitor changes in intracranial fluid content or distribution in an intensive care unit patient. Standard of care for these patients includes invasive monitors that require drilling a hole in the cranium and inserting a probe, such as an intracranial pressure (ICP) monitor, or microdialysis or “licox” probes, for measuring chemical changes to the fluids in the brain. No continuous, noninvasive measurement techniques are currently commercially available for detecting cerebral fluid changes, such as those that occur with bleeding or edema. Furthermore, many brain injuries are not severe enough to warrant drilling a hole in the cranium for invasive monitoring. Thus, for many patients with brain injury, there is no continuous monitoring technology available to alert clinical staff when there is a potentially harmful increase in edema or bleeding. Instead, these patients are typically observed by nursing staff, employing a clinical neurological examination, and it is not until changes in the fluid composition or distribution in the brain cause observable brain function impairment that the physicians or nurses can react. In other words, there is no way currently available for monitoring intracranial fluid changes themselves, and thus the ability to compensate for such changes is limited.
VIPS has been previously proposed for diagnosis of brain fluid abnormalities. Patents have been awarded for proposed devices, and promising scientific studies of prototype devices are described in the literature. For example, Rubinsky et al. described the use of VIPS for this purpose, in U.S. Pat. Nos. 7,638,341, 7,910,374 and 8,101,421, the disclosures of which are hereby incorporated in their entirety herein (referred to herein as the “Rubinsky Patents”). Wyeth et al. described additional details of the use and design of VIPS devices in U.S. Pat. No. 8,731,636, which is hereby incorporated in its entirety herein. However, no practical, mass-produced medical device based on VIPS technology has yet emerged, to provide clinicians specializing in brain treatment or other areas of medicine the promised benefits of such a device.
Ideally, a medical device solution would provide a VIPS system with improved performance, usability and manufacturability, such that it could be used for noninvasive fluid change detection in the brain and/or other areas of the body. The embodiments described herein endeavor to address at least some of these objectives.